I have a question concerning Traveler and swapping nhd files. There were three previous threads with similar questions (traveler-discussion/topic3127; chatterbox/topic3300 & traveler-discussion/topic3723). I’d be however very curious whether people have more insights regarding the Traveler mod and the swapping of nhd files in the past years. I am aware that there may be issues with custom worlds, as some lack a proper unique ID number assigned to them – so this would be something, I would have to check myself.

Here is my question:

I am currently playing in Willapa Valley with family A0. I am intending to move one of the grown-up children (i.e. family A1) to another world, e.g. Aurora Skies via Traveler.

I would intend to keep on playing in both worlds in parallel in different saves.

When my sim family A1 in Aurora Skies would like to travel back to Willapa Valley, e.g. after one-two generations – can I replace the (original) Willapa Valley nhd file in my Aurora Skies save folder with the most recent Willapa Valley nhd file, e.g. where there would have been also some one-two generation progress? To make sure that family A1 travels to the most recent version of my family A0 save in Willapa Valley.

I understand that in previous threads the issue of potential corruption was mentioned. It’s not an issue, if I was to reestablish some family tree connections with Nraas, if need be. I would just like to know whether this is possible, whether people have tried this before and what their experience has been, i.e. has there been corruption, if yes, what sort, etc.?

I would be very grateful for your insights.
I joined the Sims 3 community only last year. Thanks a lot for all your work and dedication to make this game better!

The issue, or at least the main issue, with swapping .nhd files like this is something like the old and new .nhd files may happen to assign the same ID to different sims or even objects. The current world, or I guess the TravelDB file, will have pointers that reference data in the other world.

If you remove an .nhd file entirely and let the game generate a new one, those pointers get flushed. If you replace one .nhd file with another in an ongoing save, those pointers just assign themselves to whatever items have the corresponding IDs in the new .nhd file. That's how you get cats and chairs in the family tree.

That may not be a perfect explanation, and someone else may have a better response. The underlying concept though is that you don't want a set of references to end up referring to something other than what they did originally. Allowing that to happen can definitely cause corruption.

Rather than trying to swap out .nhd files, why not do an empty travel back and forth whenever you want to play the other world? Traveler supports this, the worlds stay connected, and you can progress each one independently as you see fit. Your sims would likely lose their assigned dreams and opportunities, but they'd keep their homes, careers, relationships, and pretty much everything else.

If this doesn't work for you for some reason, I'd suggest saving the A1 household to the library and starting a completely new save with them. Then when you're ready to have them travel back, add the .nhd file for your progressed Willapa Valley into the new save and have the sims travel back.

I don't know whether it would be better to Totally Annihilate the A1 sims in Willapa Valley before doing this and then reconnect the family once they're all back in the same world. I'd probably test it out first to see whether anything weird happened if I didn't. And regardless of how you choose to proceed, a test run is in order to make sure that your custom world can be traveled back to without problems.

All of the above covers it pretty well, I'll add on to what the differences between these two methods generally are.

The main use of moving .nhd files is to consolidate saves that were already separate to begin with.
Whether it be when someone has two save files where they would now like to have sims visit one another, or if they've been making significant changes to a world and would like that version to be the one visited with Traveler.
For example, I emptied every lot in Midnight Hollow in a new save because it was quite a tedious process to try and do in the middle of a travel scenario. When it was done, I used the .nhd in my actual save so that my sims could travel directly to that modified world.

When the things you want are already together, Traveler contains a wealth of tools for switching between them. This way Sims will retain their friendships and relation to one another, and even be able to call each other and vacation in one another's worlds, which would be entirely severed the moment you loaded a save with one world removed.
There is little reason to do the first method in reverse if the end goal is for the two sets of data to be together. Taking .nhd away would only really benefit wanting to separate worlds and their residents permanently.

Thank you very much for your replies and explanations! I very much appreciate this.
I think for the moment, I will just move Sims to different worlds the regular way and when/if I make them move back to their original world, I will reestablish family tree links and a few friends via MC.